2. Read and translate the words of the same root:

To classify – classification; to transport – transportation; to explore – exploration; to produce – production; to refine – refining – refinery; to develop – development; to convert – conversion; viscous – viscosity; deep – depth; dense – density; difficult – difficulty.

3. Read and translate the following words. Pay attention to the pronunciation.

Oxygen, hydrogen, nitrogen, carbon, sulphur, hydrocarbons, method, temperature, salt, earth, viscous, mixture, condensate, volatile, asphalt, gasoline, solid, associated, geologist, combined, organic, organism, period, percentage.

4. Read the text and translate it into Russian.

Light and Heavy Crude Oil

What is oil? Together with natural gas, it makes up petroleum, which is Latin for "rock oil". Petroleum is basically a mixture of naturally occurring organic compounds from within the earth that contain primarily hydrogen, carbon and oxygen. When petroleum comes straight out of the ground as a liquid it is called crude oil if dark and viscous, and condensate if clear and volatile. When solid it is asphalt, and when semi-solid it is tar. There is also natural gas, which can be associated with oil or found alone.

Crude oil comes in many forms. Usually it is black, but green, red or brown oils are not uncommon. There are a number of classifications for crude oil which are used to divide the oil by impurities and consistency. According to one of them crude oil is divided into light crude oil and heavy crude oil.

Light crude oil is liquid petroleum that has a low density and flows freely at room temperature. Light oil has an API gravity (measure of liquid specific gravity as defined by the American petroleum institute) of 30 to 40 degrees, which means that the density is much less than 1.0 g/cc (grams per cubic centimeter). This oil floats easily on water. It generally has a low wax content. This means that the viscosity of the oil is much lower, which makes it easier to pump and transport. Light crude oil receives a higher price than heavy crude oil on commodity markets because it produces a higher percentage of gasoline and diesel fuel when converted into products by an oil refinery. Because light crude oil has so many desirable traits, it is often a very desirable product, with many refineries preferring to work with light crude oil whenever possible.

Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°. It is referred to as "heavy" because its density is higher than that of light crude oil. Heavy crude oil does not flow easily, and it is so dense that it sinks, rather than floats, in water. Physical properties that differ between heavy crude oils and lighter grades include higher viscosity and specific gravity, as well as heavier molecular composition.

Heavy crude oils provide an interesting situation for the economics of petroleum development. The resources of heavy oil in the world are more than twice those of conventional light crude oil. Large quantities of heavy crude oils have been discovered in the Americas including Canada, Venezuela and California. The relatively shallow depth of heavy oil fields (often less than 3000 feet) can contribute to lower production costs.

However, production, transportation, and refining of heavy crude oil present special challenges compared to light crude oil. The high viscosity and density makes production of heavy crude oils more difficult. Due to increased refining costs and high sulfur content heavy crude oils are often priced at a discount to lighter ones. With current production and transportation methods, heavy crudes have a more severe environmental impact than light ones.

The difficulties of production and transport of heavy oils render conventional methods ineffective. Specialized techniques are being developed for exploration and production of heavy oil. Current research into better production methods also seek to reduce the environmental impact.